Tag: head scab

Scouting Fields for Fusarium Head Blight

Alyssa Koehler, Extension Field Crops Pathologist
University of Delaware

Most barley has made it past flowering, with wheat fields approaching anthesis. Over the past few weeks we have remained at low risk for Fusarium head blight (FHB) http://wheatscab.psu.edu/. There have been some rain events this week, and we will keep an eye on the model over the next 1-2 weeks. The recommended stage for fungicide application is when 50% of main tillers are flowering (yellow anthers visible) until 4-5 days after. Once wheat has flowered, symptoms of FHB are visible in 18-24 days, but cool weather can slow symptom development. Heads with FHB will have bleached florets or bleached sections of the head (Figure 1) and may have pink growth on spikelets. Glume blotch may also be present, but typically has more of a grey appearance. You can follow these steps to assess the level of FHB present in your field.

Wheat infected with fusarium
Figure 1. Symptoms of Fusarium head blight on wheat. Image: A. Koehler, Univ. of Delaware.
  1. For every 10 acres of field, randomly select one spot to survey.
  2. Keeping your line of sight above the wheat heads, walk 40-50 yards and randomly pick 10-20 heads to look at on the plant or detach and place into a bag. (You don’t want to be looking down and biasing the heads you select).
  3. Once you have randomly collected the heads, rate the percent of each head with symptoms of FHB (bleaching or pink growth on spikelets).
  4. After you have recorded values for each head, determine the average percent FHB severity by dividing the sum of disease severities by the total number of heads collected.

(Ex. You rate 10 heads with severity values: 0, 10, 30, 0, 0, 20, 10, 0, 0, 0. These add up to 70. 70/10 heads = 7% FHB severity).

Higher levels of FHB are typically associated with elevated levels of DON and possible issues with yield and test weight. It is possible to have delayed or lower levels of symptoms and still have DON.

  1. Repeat this assessment as needed to get an overall rating for the field. Fields with greater than 10% FHB severity are at higher risk for yield losses or elevated DON. Fields with elevated DON should be harvested as early as possible and you may want to consider increasing combine fan speeds and shutter openings to reduce the amount of scabby kernels harvested.

 

Checklist for Fusarium Head Blight Fungicide Applications

Andrew Kness, Agriculture Agent
University of Maryland Extension, Harford County

As wheat approaches flowering, here is a final list of reminders/tips to make the most of your fungicide applications that are targeted to manage Fusarium head blight (head scab):

  • Use an effective fungicide. These include: metconazole (Caramba®), prothioconazole + tebuconazole (Prosaro®), prothioconazole (Proline®), and adepidyn (Miravis Ace®).
  • Apply an effective fungicide at the correct time. The most effective application window is from flowering (anthesis; Feekes 10.5.1) + about 5-6 days after. Late applications (4-6 days after anthesis) are better than early heading/head emergence (10.3) applications at reducing DON content in the grain.
  • Apply fungicides using the correct equipment. Ground applications should be made with 80-degree flat fan nozzles angled down from horizontal. For ground applications made at speeds over 6 mph, use a single nozzle angled forward, 30 degrees down from horizontal. For ground applications less than 6 mph, better coverage is achieved with dual forward and rearward facing nozzles, angled 30-45 degrees down from horizontal.
  • Sprayer should be operated to achieve droplet sizes of 300-350 microns.
  • Use 10-20 gallons of water per acre and keep the spray boom 8-10 inches above the crop.
  • For aerial applications: Use 4-5 gallons of water per acre. Fine to medium sized droplets (300-350 microns). Small aircraft should operate 8-10 feet above the crop; large aircraft 10-12 feet. Nozzles should be mounted to cover 65% of the aircraft’s wingspan and mounted as low as possible.
wheat at start of anthesis
Wheat at Feekes 10.5.1. Image: A. Kness, Univ. of Maryland

 

Fusarium Head Blight Risk: June 1, 2020

Nidhi Rawat, Small Grains Pathologist
University of Maryland, College Park

Fusarium head blight risk to susceptible wheat as of June 1, 2020. Visit www.wheatscab.psu.edu

Flowering is all finished across all counties of Maryland now, except for a few late planted fields in the northern part of MD that may still be flowering. Currently the risk of FHB is high in these areas and so FHB fungicides (Prosaro, Miravis Ace, Caramba) should be applied here. For most parts, wheat is now in the grain filling stage and should be ready for harvesting in the next couple of weeks. We experienced some showers this season, but the temperatures remained low, so symptom development in terms of bleached spikelets will be limited. It is advisable to get the DON content of the harvested grain analyzed before taking it to the market.

This is the last FHB risk commentary of the season, but feel free to contact me (email: nidhirwt@umd.edu) if you have any questions related to wheat diseases any time of the year!

Fusarium Head Blight Risk: May 25, 2020

Nidhi Rawat, Small Grains Pathologist
University of Maryland, College Park

Fusarium head blight risk to susceptible wheat varieties as of May 25, 2020. Image from: wheatscab.psu.edu.

Wheat is at the dough stage in the lower eastern and lower western shore of the state. Although, the map shows FHB risk to be high in this region, wheat is well past the stage of FHB infection and spray here. Several other fungal foliar diseases such as Septoria tritici blotch, Stagonospora nodorum blotch, glume blotch, and tan spot have been observed here because of the rains or overcast skies and low temperatures. In our experimental plots at Wye, we have even observed some specks of leaf rust and stripe rust diseases. However, the damage due to these diseases is not going to be substantial now, and growers in this region do not need to spray fungicides for controlling these diseases. In a normal year, now would be the time to start looking for bleached spikelets to assess FHB severity. However, due to the cold spring that we had this year, symptoms may develop late/may not be visible, and the DON content of the grains should be analyzed and considered as the sole basis of FHB losses. Up in the North, wheat has finished/is finishing up flowering. FHB risk for today appears to be low here, especially for a moderately resistant variety. Check the FHB risk map http://www.wheatscab.psu.edu/ to monitor the daily risk here. If you are worried about foliar diseases mentioned above, the triazole fungicides do an excellent job of controlling these diseases as well. Strobilurin containing fungicides should be avoided at this stage.

Fusarium Head Blight Risk: May 19, 2020

Nidhi Rawat, Small Grains Pathologist
University of Maryland, College Park

Screenshot of FHB risk as of May 19, 2020. Risk is low across the state
Fusarium head blight risk to susceptible wheat varieties as of May 19, 2020. Image from: wheatscab.psu.edu.

Wheat in the Eastern shore and the Southern part of Western shore of Maryland has finished flowering, except for a few late planted fields. Up in the North-western counties of the state (Frederick, Howard, Carroll, Harford) wheat is flowering currently. Past week’s low temperatures slowed the progress of wheat. Heads emerged but waited for a week or so to flower in several places. The FHB risk for Maryland does not show to be high currently. However, the unusual pattern of weather has caused several other foliar diseases to appear across the state. Fungal diseases such as Stagonospora nodorum blotch, Stagonospora tritici blotch, Tan spot, Powdery mildew and even some viral diseases such as Wheat streak mosaic virus and Soil-borne mosaic virus have been observed in wheat fields this year. It is important to remember that Strobulurin containing fungicides should not be applied at this stage. Fungicides will not be effective against any viral diseases. However, the FHB fungicides (Prosaro/ Caramba/ Miravis Ace) will be able to control the other fungal foliar diseases. These fungicides do not need to be tank mixed with another product for spraying. The fungicide products should be applied at the full rate recommended by the manufacturers. Aerial application at a rate of 5 gallons per acre or ground application at 15 gallons per acre with 300-350 um droplet size is recommended. Spray nozzles should be angled at 30°-45° down from horizontal, toward the grain heads, using forward- and backward mounted nozzles or nozzles with a two directional spray, such as Twinjet nozzles.

Fusarium Head Blight Risk: May 10, 2020

Nidhi Rawat, Small Grains Pathologist
University of Maryland, College Park

Fusarium head blight risk to susceptible wheat varieties as of May 10, 2020.

Wheat in the Eastern Shore of Maryland and Southern Maryland on the west of shore is finishing up flowering. Wheat in the Northern parts is either flowering/ will soon start flowering. The FHB risk for this part of the state (Frederick, Carroll and Harford counties) is predicted to be moderate to high, especially if the wheat variety planted is susceptible. If the planted variety is resistant, the risk is not predicted to be particularly high. The recommended stage for application of fungicides on wheat is at flowering (50% of the main tillers showing yellow anthers) or within 4-5 days of that. The fungicides effective for FHB are Prosaro/ Caramba/ Miravis Ace. These fungicides do not need to be tank mixed with another product for spraying. The fungicide products should be applied at the full rate recommended by the manufacturers. Strobilurin containing fungicides should not be sprayed at this stage. Aerial application at a rate of 5 gallons per acre or ground application at 15 gallons per acre with 300-350 um droplet size is recommended. Spray nozzles should be angled at 30°- 45° down from horizontal, toward the grain heads, using forward- and backward mounted nozzles or nozzles with a two directional spray, such as Twinjet nozzles.

Fusarium Head Blight Risk: May 7, 2020

Nidhi Rawat, Small Grains Pathologist
University of Maryland, College Park

Fusarium head blight risk to susceptible wheat varieties as of May 7, 2020.

With the recent showers in the state, the risk of Fusarium Head Blight appears to be high. In the Eastern Shore and the Southern part of the state wheat is flowering/towards the end of flowering. Growers with their wheat still flowering or are within a window of 4-5 days of flowering are advised to spray head scab fungicides (Prosaro, Caramba, Miravis Ace). These fungicides do not need to be tank mixed with another product for spraying. The fungicide products should be applied at the full rate recommended by the manufacturers. Strobilurin containing fungicides should not be sprayed at this stage. Aerial application at a rate of 5 gallons per acre or ground application at 15 gallons per acre with 300-350 um droplet size is recommended. Spray nozzles should be angled at 30°-45° down from horizontal, toward the grain heads, using forward- and backward mounted nozzles or nozzles with a two directional spray, such as Twinjet nozzles. In the Northern counties, we are still around 7-10 days away from flowering.

FHB Risk: May 3, 2020

Nidhi Rawat, Small grains Pathologist
University of Maryland, College Park

Fusarium Head Blight Risk, May 3, 2020.

Wheat in the Eastern Shore of Maryland is flowering or will do so in a couple of days. With this week’s rains, and more showers coming our way, the risk of Fusarium Head has increased significantly in this part of the state. Growers are advised to spray head scab fungicides (Prosaro/ Caramba/ Miravis-Ace) at wheat flowering (50% of the main tillers showing yellow anthers) or within 4-5 days of this stage. These fungicides do not need to be tank-mixed with another product for spraying. The fungicide products should be applied at the full rate recommended by the manufacturers. Strobilurin containing fungicides should not be sprayed at this stage. Aerial application at a rate of 5 gallons per acre or ground application at 15 gallons per acre with 300-350 um droplet size is recommended. Spray nozzles should be angled at 30°-45° down from horizontal, toward the grain heads, using forward- and backward mounted nozzles or nozzles with a two-directional spray, such as Twinjet nozzles. Up in the North, wheat is booting and still roughly around 1-2 weeks away from flowering.

Fusarium Head Blight Risk: April 26, 2020

Dr. Nidhi Rawat, Small Grains Pathologist
University of Maryland, College Park

Wheat in the Eastern Shore of Maryland has started booting and should be heading out soon. Barley is already flowering there. Note that barley does not show any yellow anthers at flowering and is prone to FHB as soon as it heads out of the boots. Wheat is considered to be at flowering when at least 50% of the heads of a field are beginning to show yellow anthers. With the recent rains FHB risk has increased to moderate/high level in the lower eastern shore counties. Growers here should keep an eye on the FHB risk in the coming days, as wheat heads and flowers here in coming weeks. Fungicides Prosaro, Caramba and Miravis-Ace should be effective in minimizing damage due to FHB in wheat, when applied at flowering. Strobilurin containing fungicides should not be applied now, as they might increase the chances of DON content in the grains. So far, no major concern from other diseases like powdery mildew or rusts has been seen in wheat in the state. Some low intensity incidences of tan spot were observed, which the FHB fungicides applied at flowering should be able to tackle. Up in the northern part of the state wheat is at second node to flag leaf stage, predictably around 2-3 weeks away from flowering.

FHB map of Maryland showing low to moderate risk of head scab
Figure 1. Fusarium head blight risk to susceptible wheat varieties on April 26, 2020.

 Let me know if you have any questions or concerns (nidhirwt@umd.edu).

Don’t Fall Asleep on Head Scab

Andrew Kness, Agriculture Agent
University of Maryland Extension, Harford County

Wheat is progressing rapidly across the state due to our mild winter. In the coming weeks, wheat will begin flowering and entering the most critical management stage for Head Scab or Fusaruim Head Blight (FHB). Scout fields as heads emerge and determine when they start to flower (yellow anthers emerging from the middle of the spike). At this stage you will need to make the call to apply a fungicide or not.

Figure 1. Left: Feekes 10.3. Middle: Feekes 10.5.1 (yellow anthers beginning flowering). Right: 4 days after anthesis (white anthers post flowering). Image: A. Koehler, Univ. of Delaware.

Right now, FHB risk is very low across the region, mostly due to the cool nights we are experiencing (Figure 2). However, conditions can turn favorable for FHB very quickly, so don’t fall asleep on it! FHB can sporulate and infect flowering spikes at temperatures in the 50s as long as adequate moisture and humidity is present.

Scab risk map as of April 21, 2020
Figure 2. Head scab risk to susceptible winter wheat varieties as of April 21, 2020.

If conditions turn wet, humid, and above 50 degrees at flowering, FHB risk will be high and you will have about a 5 day maximum window after Feekes 10.5.1 (start of flowering) to make a fungicide application to suppress DON vomitoxin. Optimal timing for a fungicide application is at Feekes 10.5.1 and up to 5 days after. University research has indicated that earlier applications at heading (Feekes 10.3-10.5) do not consistently reduce DON levels in the grain as compared to applications made at or shortly after flowering.

Even though it may seem a bit early and cool, continue to monitor the Scab Risk Tool (www.wheatscab.psu.edu/) to help you assess the risk of developing FHB in your wheat crop so that you’re not taken by surprise.

For fungicide recommendations and other application recommendations, click here.